1. Field of the Invention
The present invention relates to a drive mechanism for an electric car.
2. Description of the Prior Art
In a conventional gasoline engine car rotation generated by a prime mover or a gasoline engine is changed in speed through a transmission such as an automatic transmission or a manual transmission and transmitted to drive wheels. Since the gasoline engine creates energy by burning an air-gasoline mixture under compression, noise is produced by the combustion and, worse, the environment is contaminated by the engine exhaust gases.
On the other hand, an electric car produces neither noise nor exhaust gases. However, the electric car of the prior art is restricted in the amount of electricity which can be stored in the battery so that its cruising distance is short. In order to achieve a sufficient cruising distance, therefore, it is necessary to mount a large-sized battery. Further, a motor of a size allowing it to be mounted on an ordinary vehicle generates a lower torque than that produced by an engine so that the vehicle can neither start quickly nor run under a high load or at a high speed.
Moreover, if the electric motor is arranged coaxially with the drive shafts to run the electric car, its diameter is restricted by the required minimum road clearance.
The foregoing has led to consideration of use of motors corresponding in number to the number of drive wheels so that the individual motors may be small sized while improving the running performance of the car. To the extent that the motors can be small-sized, it is possible to reduce the weight of the car and to facilitate mounting of the motors.
However, a reduction in the size of the motors requires a reduction in the size of the rotor supporting structure, at a sacrifice of accuracy and rigidity.